1. Field of the Invention
The present invention relates to an ink jet recording method and apparatus. More specifically, the present invention relates to an ink jet recording method which can record a high quality image on a normal paper such as Xerography paper which is usually used in a Xerography copying machine or the like and apparatus therefor.
2. Discussion of the Prior Art
In a conventional ink jet recording method, a jetting energy generator, such as a piezoelectric element or an electrothermic transdoting element, is used as a jet drive source. As shown in FIG. 18, ink droplets are jetted forth through nozzles to a recording medium 100, such as recording paper, film, or cloth by the jet drive source so that an image is recorded on the recording medium 100. This ink jet recording method has many excellent advantageous features which include low noise and further, no requirement of any special fixing process capable of the recording of full color images as well as merely black and white images.
A recording paper for the ink jet recording is frequently used in the full color image recording by the above ink jet recording method. The recording paper has a coat layer which is formed by applying hydrophilic binder containing fine particles of SiO.sub.2, CaO, or the like, dispersed on a original recording paper so as to improve the absorption and fixing of ink to the recording medium to obtain a high quality image. However, the use of this special paper increase the cost to produce one sheet of print, viz., the running cost.
If papers of less ink absorption, such as Xerography papers or quality papers, usually used for Xerography copying machines, are used for the full color image recording by the ink jet recording method, several problems arise. A full color image, which is recorded on a paper of less ink absorption by using ink of the slow-dry type which can depict characters and line images of relatively high image quality, is poor in quality. As shown in FIGS. 19(a) and (b), ink droplets 101 including four color of black(Bk), cyan(C), magenta(M), and yellow(Y) are not dried quickly enough to prevent flowing of the droplets so that adjacent ink droplets are connected with each other. Accordingly, spreading of ink, called color bleeding 102, takes place among adjacent ink droplets of different colors, thereby inevitably bringing about a color mixture to deteriorate the image quality.
In a case where a paper of less ink absorption, such as Xerography paper or quality paper, and ink of relatively quick dry/penetration type are used for the full color image recording, the ink spread phenomenon among different color ink droplets does not take place. However, the following problems arises anew. As shown in FIG. 20, since ink droplets 101 deeply penetrate into the recording medium 100, little coloring materials are left on the surface of the paper. Accordingly, the print area by the ink droplets 101 is low in density and the range of the color reproduction is narrow. Further, the ink is dried in a state that it is horizontally spread in the surface of the recording medium. Therefore, the reproduced characters/lines are fatty, and deterioration of the image quality owing to the feathering is great.
Thus, in the conventional ink jet recording method, it is very difficult to improve both the full color image and the black/white image in image quality when the paper is of less ink absorption than the special paper exclusively for the ink jet recording is used. Accordingly, in the printing by the conventional ink jet recording method, those papers specially used for the ink jet recording must be used for the recording medium. Therefore, the cost to produce one sheet of print, viz., the running cost, is inevitably high. The high running cost hinders the prevalence of the ink jet recording devices.
Many practical techniques to solve the problems have been proposed. Some of these techniques will be referred to below. The ink jet recording device disclosed in Unexamined Japanese Patent Publication No. Hei. 4-355157 discloses a color ink jet recording device for recording a color image using inks of different colors, which is constructed such that the inks of those colors are prepared in their compositions so as to make the panetration of at least one ink ingo a recording medium different from that of the other inks.
The ink jet recording device disclosed in unexamined Japanese Patent Publication No. Hei. 4-364961 discloses a color ink jet recording device for recording a color image using inks of different colors by means of a plural number of recording means, which is constructed such that the inks of those colors are prepared in their compositions so as to make the fixing performance for at least one ink on a recording medium different from that for the other inks. Further, the ink recording device is operable such that a fixing rate of ink first jetted to the recording medium is higher than that of ink subsequently jet.
The conventional ink jet recording devices have several problems to be solved. The penetration difference of the ink to such an extent as in the ink jet recording device disclosed in Unexamined Japanese Patent Publication No. Hei. 4-355157 fails to satisfactorily achieve both the improvements of the image quality; elimination of the color bleeding among the image areas of different colors and realizing of a sharp image.
For the ink jet recording device disclosed in Unexamined Japanese Patent Publication No. Hei. 4-364961, constructed such that the inks of different colors are prepared in their compositions so as to make the fixing performance at least one ink on a recording medium different from the penetration of another ink, and that a fixing rate of ink first jetted to a recording medium is higher than that of ink subsequently jet, the following disadvantageous fact was empirically confirmed by the inventors of the present invention. A penetration rate of the later jetted ink C of low fixing rate when it is jetted to an already recorded area A on the recording medium is greatly different from its penetration race when it is jetted to a non-recorded area B thereof. With this great difference of the penetration rates, the ink C is irregularly pulled to the already recorded area, causing the color bleeding as shown in FIGS. 21(c). For example, an intercolor spread occurs as shown in FIG. 21(a). In addition, the circumference of characters are spread, as shown in FIG. 21(b).